As a surgical treatment for treating stricture or occlusion of a biliary tract, a ‘biliary stent placement’ is known, in which a radially expandable biliary stent is indwelled in a lesioned part. By performing the biliary stent placement, patency of the lesioned part in the biliary tract can be ensured and as a result, for example, remediation of obstructive jaundice symptoms can be achieved.
As biliary stents used for such a biliary stent placement, conventionally discussed biliary stents have a tubular stent body configured to be expandable and a membrane extending to protrude from one end of the stent body in a cylindrical manner (see, e.g., Patent Document 1). Conventional biliary stents are configured such that the membrane extends out toward a duodenum when being indwelled in a lesioned part of a biliary tract. The membrane is configured to allow bile flowed out from a gallbladder to be flowed toward the duodenum and also to prevent a backflow from the duodenum to the gallbladder. In this specification, a function of allowing bile flowed out from a gallbladder to flow toward the duodenum and also preventing a backflow from the duodenum to the gallbladder is referred as to ‘valve function’.